What are the factors that affect the rate of chemical reaction?

The five main factors that affect the rate of a chemical reaction include: 

1. The concentration of the reactants: As the concentration of the reactants – enzymes and substrates) increases, the rate of the chemical reaction also increases. This is because higher concentrations increase the frequency of collisions between the two reactants, providing more opportunities for chemical reactions to take place.   
2. Temperature: For chemical reactions to take place, the molecules of the reactants have to collide with each other with sufficient energy and in the correct orientation. Higher temperatures raise the energy levels of the molecules involved in the reaction, providing more opportunities for molecules to collide with each other, which speeds up the overall chemical reaction. At very high temperatures however, the rate of reaction starts decreasing. This is because the very high temperatures break the hydrogen bonds within the protein causing the protein to unravel and lose the shape of their active sites, so that they are unable to bind to their substrate. 
3. pH: Every enzyme works at peak efficiency at a specific pH range. Deviations from the optimum pH range break the hydrogen bonds and also affect the ionic bonding within the enzyme’s structure. This causes enzymes to become denatured and lose the shape of their active sites, decreasing the rate of the chemical reaction. 
4. Presence of a catalyst or inhibitor: Catalysts cause the reaction to proceed by a different pathway, which lowers the activation energy required for the reaction to take place, thus speeding up the rate of chemical reaction. Inhibitors also cause the reaction to proceed by a different pathway but they slow down the rate of chemical reaction. 
5. Surface area: This applies only if one of the reactants is a solid. In this case, the larger the surface area of the solid, the faster the rate of the chemical reaction. This is because there is more space for the reaction to occur. Cutting up a solid into smaller pieces is one way to increase its surface area and speed up the rate of reactions.